Multiphase electrical generators of the type which are manufactured by Westinghouse Electric Company, the assignee of this invention, commonly incorporate a plurality of stator windings, which are the high voltage AC winding armature elements that provide the generator's output voltage and current. Stator windings are formed of conductive coils, in which ac voltage is induced by the passage of the rotors magnetic flux field. Each coil commonly includes a plurality of half-coils, each half-coil extending the length of the slot in the stator and being joined to another half-coil or a phase end lead at the end turn or involute portion of the stator assembly. The end of such a half-coil 10 according to one prior art design is illustrated in FIG. 1. As may be seen in FIG. 1, half-coil 10 includes stacks 14, 16, 20, 22 of copper conductor strands and a stack 24 of vent tubes through which a coolant such as hydrogen gas is intended to circulate. The individual strands in adjacent strand stacks 14, 16 and 20, 22, respectively, are transposed to form a pair of braid like roebel bars 12, 18, respectively, to reduces losses from cross slot flux and to reduce hot spot temperatures. This process, known as roebelling, maintains relatively uniform voltage differences among strands.
In the coil ends or involutes, the effect of voltage induced by end region flux is conventionally controlled by a group transposed series connection, which is depicted in FIG. 2. Such a connection joins the strands from the first half-coil to corresponding strands in a second half-coil 26 by separating the strands into individual strand groups 28, 30, respectively, and then joining each strand group 28 with a corresponding strand group 30 in an individual series connection 32. This process is labor-intensive, time consuming and cumbersome. First, the individual strands must be separated and their strands regrouped into specified bundles. The strands must also be cleaned, tinned, bundled into clips, and soldered into the series connector 32. The purpose of tinning is to provide a uniform solder coating that will prevent voids when the strands are bundled into crimped or bolted connectors and heat fused together. The exposed strand ends are first cleaned with an abrasive wheel or by hand, and then wiped with alcohol to remove dust and other contaminates. Next, the strands are brushed with a rosinalcohol flux to prepare the copper surface for tinning. Then the copper strand ends are hand dipped into heated solder. Excess solder is allowed to drip off, and is smoothed by wiping. An alternative method, which is more reliable but far more laborious, is to apply the solder coating by hand, to each strand individually, using a soldering iron with a thermocouple attached to control soldering temperature.
Using either method, considerable skill and care are required to achieve uniform tinning. Deviations from precise temperature/time process requirements produces weak and uneven adhesion between the copper and the solder. Lumps and irregular thicknesses of solder may also be produced. When these strands are fitted into a bolted series or phase connector, their uneven coating prevents effective tightening. Cold solders may cause voids to develop between strands, which can cause the unit to fail ultrasonic inspection. In that case, the entire process must be done over. The cost of rework and delays can be considerable. Moreover, working space for tinning and connecting is cramped. These and numerous other problems occur with the present, conventional, group transposed connectors.
It is clear that there has existed a long and unfilled need in the prior art for an improved connector for connecting the strands of a phase winding half-coil in an electrodynamic system such an a multiphase electrical generator to a like half-coil, or to a phase end lead.